New EEP draft: Pinning operator ^ in patterns

[Michael P.]

On Thu, 14 Jan 2021 13:13:54 -0500
Leonard B <leonard.boyce@REDACTED> wrote:

> IE, if a variable is previously assigned within the outer scope use
> that variable within the inner scope.
> This, in my addled mind, makes more sense
>
> EG:
> %% X is from outer scope, L is from outer scope, V is local to comprehension
> X = 5.
> L = [1,2,3,4,5].
> [V || {X, V} <- L].

Done?

```
Eshell V10.2.4  (abort with ^G)
1> X = 5.
5
2> L = [1,2,3,4,5].
[1,2,3,4,5]
3> [V || {X, V} <- L].
[]
4> [{X, V} || V <- L, V /= X].
[{5,1},{5,2},{5,3},{5,4}]

5> Lt = [{1, 2}, {2, 3}, {4, 5}, {5, 6}, {6, 7}, {5, 8}].
[{1,2},{2,3},{4,5},{5,6},{6,7},{5,8}]
6> [V || {X, V} <- Lt].
[2,3,5,6,7,8]
7> [V || {Selector, V} <- Lt, Selector == X].
[6,8]
```
Names should be swapped (X, Selector).

Naming is a burden; but also an opportunity.

~M

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